Maybe Kras is not a mutation - but a gene that is getting expressed because of inflammation
http://www.ncbi.nlm.nih.gov/pubmed/16288213
Here is a study saying k-ras gene mutation causes either pancreatic or lung or colon cancer...
http://www.ncbi.nlm.nih.gov/pubmed/10757118
Here is another article that talks about the Kras gene... And how it is also found with people with lung cancer!
http://www.sciencedaily.com/releases/2012/01/120131092412.htm
When you read about Kras... I would try the drugs that target it